Lecture topics Nematodes 2 BVM&S Parasitology T.W.Jones The Ascarids Migratory & non-migratory species Hypobiosis Paratenic hosts The Strongyles Tissue feeders Migratory & non-migratory species The Hookworms Blood feeders Skin penetration Nematodes #2 2 Main features of the Ascarids Nematodes with a simple mouth enclosed by three lips. Males lack a bursa The infective stage is the L 2 larva enclosed in the thick-shelled egg. Often have paratenic hosts. Important parasites of Pigs, horses, poultry, cats, dogs and humans. Nematodes #2 3 Gut lumen L 5 Gut, liver or lung L 4 L 3 Gut, liver or lung Ascarid life cycle Adults Gut lumen Egg L 1 L 2 In egg On ground In egg Nematodes #2 4 Groups that you need to know about Important examples of nonmigratory ascarids The Ascarids Migratory Non-migratory Ascaris Toxascaris Parascaris Toxocara Heterakis Ascaridia Dogs & cats Toxascaris Poultry Ascaridia Heterakis Nematodes #2 5 Nematodes #2 6 1
L2 hatches from egg L2 migrates to liver L2>L3 moult in liver Gut Ascaris suum L3 migrates to lungs L3>L4>L5>Adult L3 enters trachea L3 coughed up and swallowed Eggs Nematodes #2 7 Toxocara sp Large white worm (~10cm) found in the small intestine of dogs and cats. T.canis - dogs. T.cati (T.mystax)- cats. Hepato-tracheal and somatic migration Hypobiotic larvae Endogenous transplacental infection Nematodes #2 8 L2 hatches in gut Toxocara canis Gut L3>L4>L5>Adults Eggs L2 inhibited in somatic tissues After 3 months of age Liver L2>L3 moults in lungs Up to 3 months of age Trachea Nematodes #2 9 Nematodes #2 10 T.canis an important zoonosis Causes visceral larva migrans. Effects usually limited to the liver but can affect other organs such as the eye. Infection by ingestion of infective eggs from dog faeces leading to larval migration. Children at particular risk from close contact with dogs or areas that are contaminated with dog faeces. Nematodes #2 11 Toxocara cati (mystax) Life cycle similar T.canis Transmission principally transmammary Ingestion of a paratenic host containing L 2 Prenatal infection does not take place - compare with T.canis Nematodes #2 12 2
The Strongyles Tissue feeders with large buccal capsule Bursate Infective form = ensheathed L 3 on pasture Migratory and non-migratory species Important parasites of Ruminants Equines Adaptations for tissue feeding Large buccal capsule Cutting plates Teeth Sometimes called plugfeeders Nematodes #2 13 Nematodes #2 14 Important examples of strongyles of ruminants Chabertia - Intestinal worm of sheep & cattle Strongyles of equines Adults Small strongyles aka cyathostomes Large intestine Large strongyles Large intestine Infective form Ensheathed L 3 Ensheathed L 3 Oesophagostomum - Intestinal worm of sheep & goats Nematodes #2 15 Larval behaviour Number of species Develop in nodules in the intestinal wall 15 Somatic migration 3 - Nematodes #2 16 Gut surface - plug feeders Gut surface - feeds on blood L 4 Fibrous nodules in gut wall Equine cyathostomes L 5 L 3 Adults L 3 L 2 Gut lumen Egg L 1 Free-living On pasture Free-living L3 on pasture L3 enters mucosa Somatic migration Sp. L3>L4 moult Gut L5>Adults Extra-intestinal stages L4>L5 moult L5 return to gut wall Eggs Nematodes #2 17 Nematodes #2 18 3
Species vulgaris edentatus equinus sp - migratory patterns Location of first moult Submucosa Liver Gut musculature Location of second moult Cranial mesenteric artery Flanks & hepatic ligaments Gut parenchyma Controlling equine strongyles Anthelmintics Timing Active ingredient Adults Larvae especially migratory species Rotate active ingredients to combat drug resistance Pasture management Removal of faeces Harrowing of paddocks Rotational grazing Pasture resting for 6 months Alternative species grazing e.g. sheep Nematodes #2 19 Nematodes #2 20 Main features of the the hookworms Parasites of the intestine of most higher mammals other than horses. Prominent dorsal bending of the head - hook. Buccal capsule armed with broad cutting plates or teeth. Blood feeders. The L 3 enters either orally or in some cases percutaneously. Important examples of hookworms in UK Bunostomum - found in the small intestine of ruminants. Uncinaria northern hookworm of dog, cat & fox. Ancylostoma tropical canine hookworm coming soon to a practice near you? Nematodes #2 21 Nematodes #2 22 Ascarids Mouth surrounded by three lips Thick walled egg Nematodes #2 23 Nematodes #2 24 4
Ascaris infection from pig White spot liver Nematodes #2 25 Nematodes #2 26 Toxascaris Ascaridia Nematodes #2 27 Nematodes #2 28 Toxocara Damage to arterial wall by S.vulgaris larvae Damage to intestinal wall by S.equinus larvae Nematodes #2 29 Nematodes #2 30 5
Hookworms Bunostomum Nematodes #2 31 Nematodes #2 32 Male of Chabertia Treatment regimes for equine nematodes Buccal capsule Bursa with spicules Nematodes #2 33 Nematodes #2 34 Pasture cleaning the easy way Each horse can produce up to nine tons of waste per year! Claimed to be able suck nematode larvae from the pasture! Nematodes #2 35 6